That is the correct striker for a 47-50 truck. This is always a bit of an exercise getting these to work. Lots of adjustment both hinge, striker and latches to get it right. This is the later 52' on latch.
http://www.classicparts.com/1952-63-Door-Striker-Pair/productinfo/18%2D629A/#.UXQZY8u9KSM
This may help reading this.
http://www.stovebolt.com/techtips/doors/latch_1947_51.html